- Clinically unstable patients (within one month of exacerbation), those with a permanent pacemaker (which is a contraindication to magnetic stimulation), or significant co-morbidity, patients with an accepted indication for ACE inhibition (left ventricular dysfunction, diabetes) or a contraindication such as renovascular disease; creatinine clearance (estimated) <50); hypotension; use of anticoagulants (contra-indication to biopsy) or ACE-I or ATII receptor antagonists.